1. Field of the Invention
The invention relates to a capacitance charge device that is applied to a power system of a portable electronic product and, more particularly, to a capacitance charge device with adjustable clamping voltage capable of clamping the battery voltage so that the voltage will not have a tremendous drop instantaneously when the battery is charging the high-farad capacitance.
2. Description of the Related Art
With development of the information industry, many portable electronic products, such as a mobile phone, notebook computer, personal digital assistance (PDA), and digital camera, have been applied in daily life for different purposes such as video/audio multimedia communications and information network transmissions.
On the other hand, low working voltage has been a developing trend pursued by electronic products. Usually, a battery 10, as shown in FIG. 1, will be connected in series to a high-capacity capacitance 12 in a power system to prolong a battery's lifespan. The capacity of the capacitance 12 often lies between 1 and 10 farad. When the capacity of the capacitance 12 is at zero, the battery 10 will rapidly charge the high-farad capacitance 12 instantaneously and therefore cause the voltage of battery 10 to drop in large amount. In turn, the dropping of the voltage will affect not only the lifespan of the battery, but also the normal running of the system, and if the system is down, the electronic product will fail to function normally.
To cope with the problem, as shown in FIG. 2, a conventional solution is to add in a current limiting resistor connected in series between the battery 10 and the capacitance 12 in order that the resistor 14 can refrain the battery 10 from rapid discharging and thus improve the problem of the battery's tremendous voltage drop. Nevertheless, the lifespan of the battery 10 will still be affected by the natural consumption of the resistor 14.
Therefore, the invention provides a capacitance charge device with adjustable clamping voltage to solve the above-mentioned problems.